Q: How to compare the differences between 2 tiff pictures, generate a new tiff picture, and mark the differences I have two orthophoto maps (tif format) taken on different dates. How can I distinguish the differences on the two maps and mark the different points?

A: try use gdal gdalcompare.py. The gdalcompare.py script compares two GDAL supported datasets and reports the differences. In addition to reporting differences to the standard output the script will also return the difference count in its exit value.
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